Using a stage heater as opposed to a precision micro-environmental control system such as the FCS2, FCS3, or Delta T system is the Z axis shift that is a natural consequence of using peripheral heat. Staying in focus for viewing or imaging becomes highly frustrating. The heat that is applied to the area surrounding the dish that the sample rests in radiates inward toward the sample to provide warmth. However, heat doesn’t only radiate to the sample and also warms everything it is in contact with such as the stage adapter, the stage, and ultimately any other microscope parts it comes in contact with. This causes thermal expansion and, therefore, focus shifts.
When a material is heated it expands. This is why other “stage heaters induce thermal drift. However, within the heated core components of the Stable Z, there is a nodal plane from which thermal expansion occurs. The perimeter of the Stable Z’s heated core, which is also the mechanical support surface for the heated core, is machined to this nodal plane. Then the specimen resting surface is machined down to the same level. The exposed nodal plane is attached to a glass plate having a near zero coefficient of expansion and poor thermal conductivity. Therefore, heat produced in the core of the device is isolated from the microscope. Therefore, even though heat is being applied to the specimen from a metal, peripherally located source, the effect of thermal expansion is not transmitted to the specimen plane because the support surface, nodal plane within the heating core, and specimen are all coplanar with each other and stay that way!
The Stable Z Stage Adapter
The Stable Z stage adapter has multiple features over a traditional stage heater. First the adapter plate that interfaces the microscope stage is made of Zerodur ceramic which allows for nearly zero thermal expansion. It also aids to prevent heat transfer to the stage with low thermal conductivity. Secondly only the specimen retainer is heated which allows the system to be significantly more efficient. Third the specimen surface is coplanar with the support surface of the dish, which nullifies any thermal expansion that may occur. Finally, the thermal expansion ring on the stage is adjustable in height to nullify any thermal expansion from occurring as each dish has a different height specimen plane. Stage adapters are available for all major microscope stages, 110 mm, and 108 mm round adapters to 128x86mm for multi-well / SBS / SLAS footprints. This makes transition from microscope to microscope easy.
The heated specimen retainer is made of a minimal thermal mass and efficiently heated to minimize conductive and radiative heat transfer to the microscope stage.
There is also a means of adjusting the relationship between the specimen plane and the support surface for the heated core to compensate for the position of the specimen plane in various brands of dishes.
The glass carrier plate that supports the heated components does not contribute to Z axis drift because it has a near zero thermal expansion coefficient. The result is the most stable and economical method of warming a specimen for time-lapse imaging. The only limitation is that as heat is applied peripherally. Therefore, you can expect a thermal gradient, but no more or less than any other traditional “stage heater” that does induce Z-axis drift.